.308 AR - Wrong Primer - Blew Firing Pin Out of Bolt Carrier

[Load Master]

I learned something new about Sellier & Bellot primers. Their large rifle primer comes in two different flavors. There is the 5.3 LR and 5.3 LR-SE. S&B's usage chart shows the LR-SE is needed for .308 Win. I'm sad to say I proved them correct at my latest range day. No major damage, but it put a quick end to the day of load development.

With the next step up in charge level, two rounds fired of the 10 round set I had a primer blow out. It blew the firing pin totally out of the bolt carrier. The firing pin found its way below the bolt and protruding into the magazine well as can be seen here.



In the photo below the case on the left shows the primer is still intact, the concave area from the fire pin hit. The one on the right you can see it was totally punch threw and the concave part is flipped and facing into the case. This allowed enough pressure to bleed back to blow the firing pin clear past the retaining pin shown. I'm going to install one of the solid type firing pin retainers and I will no longer use the Sellier & Bellot 5.3 LR for .308 Win.



As far as the charge level, this was well within the published data. The round that caused this recorded 2675 fps of the Match King HPBT 175 gr bullet. Also, the red around the primer is from a Sharpie. I use them to identify the load.

Sellier & Bellot Primer use chart:

 

[higgite]

As far as the charge level, this was well within the published data. The round that caused this recorded 2675 fps of the Match King HPBT 175 gr bullet.

What was the MV for the previous test charge that didn't blow any primers? I could be wrong, but right offhand that seems like an awfully quick MV for that bullet in an AR-10, being gas operated and all. What length barrel does it have? Does that MV jive with your loading manual?

 

[Slamfire]

Holy Armalite Batman!

I have never seen a blown firing pin on any AR action, be they 223 or 308. EEK!

 

[wally]

I'm going to install one of the solid type firing pin retainers

Personally, I'd just keep a few cotter pin type retainers in the range bag for a quick repair if you are worried about it happening again. Better than maybe breaking the firing pin on a solid retaining pin or getting it bent enough to lock things up but good. I doubt Stoner considered a pierced primer an impossibility and would have attempted to minimize the damage should it happen.

The cotter type retaining pin always seemed a little cheesy to me until I saw this which now makes it look like it was a great choice!

 

[Load Master]

Personally, I'd just keep a few cotter pin type retainers in the range bag for a quick repair if you are worried about it happening again. Better than maybe breaking the firing pin on a solid retaining pin or getting it bent enough to lock things up but good. I doubt Stoner considered a pierced primer an impossibility and would have attempted to minimize the damage should it happen.

The cotter type retaining pin always seemed a little cheesy to me until I saw this which now makes it look like it was a great choice!

Excellent point. Hmm, maybe I should just get a few extra cheesy ones too. I'm expecting not to have the issue again by using the recommended LR-SE primers or the CCI BR-2 I also have.

 

[mstreddy]

Wow! that's good to know. I will have to check my S&B primers now. I was not aware that they had 2 different large rifle primers and how they break down the recommended usage.
Thanks for the chart info.

 

[Load Master]

What was the MV for the previous test charge that didn't blow any primers? I could be wrong, but right offhand that seems like an awfully quick MV for that bullet in an AR-10, being gas operated and all. What length barrel does it have? Does that MV jive with your loading manual?

The test rounds prior to the issue had 2721 ft-lb and the one with the failure was 2775 ft-lb of kinetic energy.

 

[Load Master]

Here is a closer look at the primer. I touched the center of the failed primer and the center pin strike piece fell in. The anvil is keeping it from fully falling in.

 

[HankC]

The load is hot, can see the ejector marks! AR10s are typically over gassed already, do you really need to run the load hot? 2675 fps - 175 gr is near the max load.

 

[FLIGHT762]

I would like to see what your powder is and charge weight are. I have a first production SR-25 I have been reloading for since 1993 and a newer GAP 10 for the past 3 years. I only shoot hand loads out of these rifles These rifles cannot take same loads like my bolt 308 Win. rifles can.

The SR-25 has a 24" barrel and it starts showing pressure signs when getting 2600 + FPS with a 175-178 bullet. I have had a few blown primers over the years and the culprit was always too much powder.

 

[Walkalong]

Holy Armalite Batman!

Indeed. Who would put out LR primers that can't be used in .308? If they can't be used in .308 I imagine that rules out a great many rifle calibers. I'm glad I didn't buy any. I bought SR, LP, and SP to try out.

 

[Walkalong]

Just looked. I have two different SP primers 4.4 Boxer & 4.4 SP Boxer. I don't see the first on that chart, and I see the second one isn't recommended for .40 S&W. Crap. No more S&B for me.

 

[243winxb]

"Load Master" I think NOT.

Todays problem , added to the case separation from before, should tell you something.

https://www.thehighroad.org/index.php?threads/308-win-how-many-reloads-before-case-failure.822768/

And then we have this one- https://www.thehighroad.org/index.php?threads/pistol-primer-for-rifle-not-a-good-idea.803440/

Be safe . Good luck.

 

[Load Master]

"Load Master" I think NOT.

Todays problem , added to the case separation from before, should tell you something.

https://www.thehighroad.org/index.php?threads/308-win-how-many-reloads-before-case-failure.822768/

And then we have this one- https://www.thehighroad.org/index.php?threads/pistol-primer-for-rifle-not-a-good-idea.803440/

Be safe . Good luck.

Fair enough. That's why I put procedures in place not to mix up primers. The first one was a bad case. The point of this post was to point out that Sellier & Bellot makes two different Large Rifle Primers. I didn't realize this. I thought maybe others may not as well.

 

[Load Master]

The load is hot, can see the ejector marks! AR10s are typically over gassed already, do you really need to run the load hot? 2675 fps - 175 gr is near the max load.

I'm well within the published data from multiple sources.

 

[Nature Boy]

I'm well within the published data from multiple sources.

View attachment 758238

But, there's a reason the often repeated "start low and work up" applies. Every rifle is different. I have a load for one of my .308 bolt guns that showed pressure signs 2g below hodgdon's published max. I have a different .308 bolt gun with a very accurate load that's 2g over Sierra's published max showing no pressure signs.

Both of those I worked up from low to high.

I would consider 2,675 FPS for a 175g bullet to be a warmish load in a bolt gun and my .308 bolt guns will handle pressures that I would consider way too hot (or too slow) for my gas operated M1A. I'm sure similar considerations should be made for an AR10.

 

[Load Master]

But, there's a reason the often repeated "start low and work up" applies. Every rifle is different. I have a load for one of my .308 bolt guns that showed pressure signs 2g below hodgdon's published max. I have a different .308 bolt gun with a very accurate load that's 2g over Sierra's published max showing no pressure signs.

Both of those I worked up from low to high.

I would consider 2,675 FPS for a 175g bullet to be a warmish load in a bolt gun and my .308 bolt guns will handle pressures that I would consider way too hot (or too slow) for my gas operated M1A. I'm sure similar considerations should be made for an AR10.

I appreciate your input and it is all good info. What seems to be missing, this wasn't a start load, this is 40 rounds into a load development and yes, it was started much lower than these last two shown. The first were 2550 fps.

Again, the intent of the post was to identify that Sellier & Bellot makes two different Large Rifle Primers. No where on the box does it indicate the one, LR isn't designed for use in .308 Win. The LR-SE is. I was getting primers that were push out at the pin strike area with even the start load levels. I thought maybe others that didn't know about the LR-SE might be interested.

 

[HankC]

Sellier and Bellot website does not show LR-SE anymore. At one time they do offer SE, likely for magnum or hot loads.
http://www.sellier-bellot.cz/en/product/components/primers/

 

[243winxb]

Wrong primer chart. Deleted.

 

[Load Master]

Sellier and Bellot website does not show LR-SE anymore. At one time they do offer SE, likely for magnum or hot loads.
http://www.sellier-bellot.cz/en/product/components/primers/

Well, apparently there is a difference in where you look for their data. The chart shown is from their US division. http://www.sellierbellot.us/index.php/download_file/view/675/163/

 

[mstreddy]

I looked over the 1K box of LR primers from S&B and I can not find anything near the product numbers listed above. It does have LR Boxer 5,3. But no product number on either the box or the 100ct tray packaging.

Walkalong, according to this new chart the small pistol will work for all SP including 40 S&W.

 

[FLIGHT762]

I don't know why you're so reluctant to post your load. I'll tell you this, if you use 45.0 grains if IMR 4064 (which is within published data) with a 175 Sierra OTM, in a gas gun, you're going to blow primers with L.C. brass. For years, the duplicate load for the Federal 175 Gold Medal Match has been 41.7-.8 grains of IMR 4064 powder. If you're loading much more than that for a gas gun, you're going to have issues.

 

[243winxb]

The chart shown is from their US division.

It sure is , Thank you

 

[mstreddy]

After looking through the US site, yes, that chart comes up, but in their catalog they only list one type of LR primer. It's surely confusing.

 

[Load Master]

After looking through the US site, yes, that chart comes up, but in their catalog they only list one type of LR primer. It's surely confusing.

It surely is. In my quest to find more information I ran across this. Has nothing to do with LR primer for .308 Win, but it tells what their primers are made of in detail if anyone has an interest. LINK